A2 ICT Revision

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Transcript of A2 ICT Revision

3.1 Databases3.4 The User InterfaceImage by Tom Mooring3.3 Software DevelopmentA2 ICT Revision3.2 Networked SystemsData Consistency: is when data is consistent and there is not more than two entries.

Data Integrity: refers to the completeness and accuracy of the data.

Data Redundancy: storing multiple times in multiple locations.

Data Independence: is the type of data transparency that matters for a centralised DBMS.What is a database?A database is an organised, structured collection of relevant data. Main features (Tables, Forms, Queries, Reports)NormalisationThe process of refining the structure of a database to minimise redundancy

and improve integrity.1NF: 2 tables2NF: 3 tables3NF: 4 tablesEntity-Relationships Diagrams (ERDs)A diagrammatic representation of the relationship between entities.Databases are designed using ERDs where tables store entities that share attributes.One-to-oneOne-to-manyMany-to-manyRelationshipsDatabase Management Systems (DBMS)The software used to manage the operation of databases.Components:Provide an interface between programsEnable data protection- levels of access, passwordsFacilitate maintenance of data dictionary

Database Administrator (DBA)A DBA will:Decide how data is stored and organised.Ensure data is secureEnsure new users are given access to appropriate dataA DBMS must allow users to:Maintain or update tablesRun macrosAllow users to print informationManagement Information Systems (MIS)This is a system which is designed to provide managers with all the information they need in order to run their organisation effectively.Factors affecting quality of information:AccurateUp to DateCompleteRelevantPresented EffectivelyImportance of information

OPERATIONAL:

decision making on a daily basis.TACTICAL:

responding to market forces and the actions of competitorsSTRATEGIC: medium and long term planningPurpose of a typical MIS:Convert data into informationEnsure information is communicated appropriatelySources of InformationInternal DataThis is data whose source and destination are within a single organisation.External DataData created within an organisation then outputted to an external destinationDecision Support Systems(DSS)Features:Supports a variety of decision making processes and stylesAssists decision making within dynamic business conditions.A set of integrated tools designed to help in problem solving

Expert Systems(ESs)An application that carries out a task near the skill level of the expert.Features:Limited to a certain areaCapable of learning from experienceBased around rules, facts and principalsKnowledge Base:a source of facts, rules and principals from a given fieldInterface Engine:solves a problem by applying the rules and knowledge already in the system to the facts that are entered concerning the problem.User Interface:includes menus, graphics and facilities for explaining the systems reasoningThreats to Data SecurityNational disastersOperator errorThreats from the internetUnauthorised access to premisesDisgruntled ex-employeesManaging security in a DBMSUser ID/ PasswordsLimiting loginsAccess Rights and lockingAudit trailsAuditing and accounting: software automatically maintains a log of all database activity. Changes can be undone to restore the original data.Disaster Recovery PlanningDef:A self contained section of a security policy that describes how all data can be recovered in the event of a natural or man-made catastropheIt should:Ensure all files are backed up at intervalsState how long backups are heldState how and where State the media usedBackup StrategiesFull Periodic BackupAll data files being copied to a separate portable storage device at regular intervalsTime consuming recoveryTransaction Logging and the Grandfather- Father-Son CycleA continuous record of all transactions made on a particular dayIncremental BackupInvolves backing up of all files that have changed at set intervalsOnline BackupSaving work on a primary and a secondary server to provide duplicate storage.Cannot recover data when it has been lostPrimary KeysA field that is used to uniquely define a particular record in a table.Foreign KeysA field in one table which is the primary key of another.Used to establish a relationship between the tables.Recovery StrategiesA disaster recovery strategy should:state the key business functions to be recovered.state the contact details appointed to helpstate the hardware, software, communications, data, personnel, essential for the businessstate the procedures to be followed before, during ,after a disasterstate how parts of the network and files will be restoredTypes of NetworkClient ServerA client is a program or hardware device that requests a service from a serverThin Clients: a computer program which depends heavily on some other computer to fulfil a role.Fat Clients: as much software is held on client PCs and a central server is concerned with data storageA Client:initiates data requests from a serverwaits for a response + acts on itconnects to several servers simultaneouslyA Server:waits for clients to request datamay accept connections from many clients simultaneouslydoesn't interact with end usersPeer-to-Peer NetworksMade up of nodes that are considered to have equal statusA P2P system:the requesting peer (RP) sends a request for data to it's neighboursthe request is flooded through network + info about suitable peers is returned to RPthe RP initiates transfer directly from selected peersdownloaded files are held on the RP.Centralised DatabaseEasier to maintainless expensive to installif a single database fails data may become inaccessibleif someone gains unauthorised access to a central server they gain access to the entire databaseDistributed Databasea centralised database is useful to firms based on only one sitein a distributed database computers may be needed at headquarters to maintain sensitive data Problems associated with remote access: network response slows when WAN traffic is heavydata is unavailable when a failure occurs on the networkMobile and Wireless CommunicationWireless (LAN)CommunicationOpen Systems Interconnection (OSI)Detecting and correcting data transmission Methods of ensuring data securityTerminal Security3.5 User Support and Training3.7 ApplicationPresentationSessionTransportNetworkData LinkPhysicalCommunication partners identifiedTransforms data into a form the application will acceptEstablishes, manages and terminates connections between applicationsTransfer of data between end systems or hostsProvides switching and routing technologiesData packets are encoded and decodedProvides the hardware means of sending and receiving data on a carrier.defines a networking framework for implementing protocolsParity bitsEcho CheckingChecksumIn each byte, 7 bits=data, 8th bit is parity bit.At receiving end a check on each byte is performed and if parity has changed the receiver knows an error occurred.

Received data is transmitted back to the sender where it is checked against the original documentNo way of knowing how and where the error occurred.Access rights and LockingUsername and PasswordsLog on restrictionsTerminal locking and PasswordFirewallsEncryptionprevents users from accessing data they don’t need to access.form the most invisible part of many systems security.restricts where the users can log on.restricting login within working hours.terminal can be locked. If forgotten a protected screensaver should activate.make a PC or a network appear to not exist to unauthorised users to gain access through the Internet. is used to store data that cant be decoded without a password.The end user is involved in:The analysis stageThe acceptance stageThe review stageIt is a linear modelMinimal resources required to implementDocumentation produced at each stageCant go backUntil the final stage of development cycle is complete a working model doesn’t lie in the hands of the clientPrototypingA throwaway prototype is built to understand the requirements.Prototype is developed based on the currently known requirements.Development of the prototype undergoes design, coding and testingRapid Application Development (RAD)Requirements Planning: combines elements of the systems planning and analysis phases of the SDLCDocumentationNon-TechnicalProject ManagementProject planning: a project must be planned + broken into smaller work tasks with time estimates.

Risk analysis: must outline the risks: scenarios that could lead to project failing.

Staff availability : will the right people be available to carry out the tasks?

Budget control: project must be profitable, all spending must be justified+ development costs under control

People management: team members must remain motivated and focused on the objective.Computer Aided Software Engineering (CASE)Normally contain components for:Modelling a system: graphics tools can be used to construct DFDs + ERDsData dictionary development and control: data dictionary is a file containing a description of data structureInterface generator: this allows the automatic creation of a user interface such as a menu, dialogue box and reportDeveloping new softwareOff- the-shelfTestingAlphaBetaAcceptanceErrors can be detected earlierQuicker user feedbackMay increase complexity of the systemUser Design: use a combination of JAD techniques and CASE toolsConstruction: programming, application development, coding and system testingCutover: SDLC implementation phaseTechnicalWill be aimed at non-ICT specialists- is often used to refer to the user guideA process of review must be undertaken to ensure its free of jargon.Will rarely leave the developers unless it's been distributed to a partner firmThe Waterfall ModelCalculated by adding together all the bytes in a packet of data which is sent as part of the data. It is then recalculated, if checksum is incorrect the data is likely an errorMobile CommunicationThis connects computers over a small geographical area.All network computers are equipped with wireless network interface cards (WNIC).Radio frequency waves are used for communication information.When a mobile connects to a network it communicates with the nearest base station.Accounting SoftwareAudit Trailsrecords each event within a system

If a hacker enters a system everything they do is logged

Log files show what someone has did and when – if a person damages data they can be apprehended.

Are needed:

To meet formal or legal audit requirements

For billing purposes

For maintenance reasons

For security reasonsImproves software quality by performing error checkingWill automatically produce documentationEnd Users:People who use computer systems on a daily basis.European Computer Driving License (ECDL)Training courses may be specific to the software they are using.Software licences are often for a set length of time. If a company wants to continue using the package, regular fees must be paid.Upgrade costs may be unavoidableServer software upgrades may be required to permit the full functionality of modern applications for effective data sharing via a network.In-house developmentA company has programmers on its staff and develops software internallySatisfy unique business requirementsRequire less technical development staffCustomising a Software PackagePurchase a basic package vendors will customise Direct negotiationPaying for the changesMake your own modificationssoftware testing continues until agreement reached between developer + purchaser.final stage before system is accepted. Testing system with data supplied by system purchaser.package distributed to potential users who test and report faults